Converts "below" to link to section it refers to.

Which would close #1883. Incidentally, it works towards solving #1416
by adding a reference to **@. The second concept mentioned there, **%
is not actually documented, but we can document it right there.

doc/Type/Signature.pod6

@@ -499,7 +499,7 @@ is not available inside the called function.
 
 Slurpy parameters have special behaviors when combined with some
 L<traits and modifiers|#Parameter_Traits_and_Modifiers>,
-as described below.
+as described in L<the section on slurpy array parameters|/type/Signature#Types_of_Slurpy_Array_Parameters>.
 
 =head2 Types of Slurpy Array Parameters
 
@@ -534,7 +534,7 @@ a(($_ for 1, 2, 3));       # OUTPUT: «[1, 2, 3]»
 A single asterisk slurpy flattens all given iterables, effectively hoisting any
 object created with commas up to the top level.
 
-=head3 Unflattened Slurpy
+=head3 X<Unflattened Slurpy|parameter, **@>
 
 Slurpy parameters declared with two stars do not flatten any L<Iterable|/type/Iterable> arguments
 within the list, but keep the arguments more or less as-is: